Yield reduction of most agricultural crops in acid soils is correlated with increasing concentrations of free aluminum in the soil solution. In wheat (Triticum aestivum), Al{sup 3+} accumulates in the root tips inhibiting their growth. Two-dimensional gel electrophoresis analysis of proteins isolated from the root tips indicates that Al{sup 3+} induces changes in the accumulation of soluble proteins in both susceptible and tolerant wheat cultivars after 24h of Al{sup 3+} treatment at concentrations that inhibit root growth. To determine whether or not these proteins are accumulated as a result of gene activation, RNA will be extracted from the tips ofmore » control and treated roots and translated in vitro. The translated proteins will be analyzed by 2-D gel electrophoresis. Possible mechanisms of Al{sup 3+} tolerance and toxicity in wheat will be discussed.« less

Control of rhizosphere pH and exclusion of Al by the plasma membrane have been hypothesized as possible mechanisms for Al tolerance. To test primarily the rhizosphere pH hypothesis, wheat cultivars, which differ in Al tolerance, were grown in either complete nutrient solution or 0.6 millimolar CaSO{sub 4}, with and without Al at pH 4.50. A microelectrode system was used to simultaneously measure rhizosphere pH, K{sup +}, and H{sup +} fluxes, and membrane potentials (E{sub m}) along the root at various distances from the root apex. In complete nutrient solution, the rhizosphere pH associated with mature root cells (measured 10-40 millimetersmore » from the root apex) of Al-tolerant Atlas 66 was slightly higher than that of the bulk solution, whereas roots of Al-sensitive Scout caused a very small decrease in the rhizosphere pH. In CaSO{sub 4} solution, no significant differences in rhizosphere pH were found between wheat cultivars, while differential Al tolerance was still observed, indicating that the rhizosphere pH associated with mature root tissue is not directly involved in the mechanism(s) of differential Al tolerance. In Al-tolerant Atlas 66, growth in a CaSO{sub 4} solution with 5 micromolar Al (pH 4.50) had little effect on net K{sup +} influx, H{sup +} efflux, and root-cell membrane potential measured in cells of mature root tissue (from 10-40 mm back from apex). However, in Al-sensitive Scout, Al treatment caused a dramatic inhibition of K{sup +} influx and both a moderate reduction of H{sup +} efflux and depolarization of the membrane potential. These results demonstrate that increased Al tolerance in wheat is associated with the increased ability of the tolerant plant to maintain normal ion fluxes and membrane potentials across the plasmalemma of root cells in the presence of Al.« less

Mucopolysaccharidosis type I (i.e., Hurler, Hurler-Scheie, and Scheie syndromes) and type II (i.e., Hunter syndrome) are lysosomal storage disorders resulting from {alpha}-L-iduronidase (IDUA) deficiency and iduronate-2-sulfatase (IDS) deficiency, respectively. The a priori probability that both disorders would occur in a single individual is {approximately}1 in 5 billion. Nevertheless, such a proband was referred for whom clinical findings (i.e., a male with characteristic facies, dysostosis multiplex, and mental retardation) and biochemical tests indicated these concomitant diagnoses. Multiple techniques, including automated sequencing of the entire IDS and IDUA coding regions, were employed to unravel the molecular genetic basis of these intriguing observations.more » The common IDS mutation R468W was identified in the proband, his mother, and his sister, thus explaining their biochemical phenotypes. Additionally, the proband, his sister, and his father were found to be heterozygous for a common IDUA mutation, W402X. Notably, a new IDUA mutation A300T was also identified in the proband, his sister, and his mother, accounting for reduced IDUA activity in these individuals; the asymptomatic sister, whose cells demonstrated normal glycosaminoglycan metabolism, is thus a compound heterozygote for W402X and the new allele. This A300T mutation is the first IDUA pseudodeficiency gene to be elucidated at the molecular level. 37 refs., 7 figs., 3 tabs.« less